Alexis Ribas

Geography and host biogeography matter for understanding the phylogeography of a parasite.

The co-evolution between hosts and parasites has long been recognized as a fundamental driver of macro-evolutionary patterns of diversification. The effect of co-differentiation on parasite diversification is, however, often confounded by underlying geographic patterns of host distribution. In order to disentangle the confounding effects of allopatric versus host speciation, the mitochondrial cytochrome b (cyt b) gene was sequenced in seventy individuals of the parasitic nematode genus Heligmosomoides sampled in the six Apodemus mice species common in the western Palearctic region. The nuclear internal transcribed spacers (ITS) 1 and 2 were also sequenced in fifteen parasites to confirm the mitochondrial data. All lineages differentiated according to a geographic pattern and independently from the sampled host species. This suggests that host speciation did not involve concurrent parasite speciation. However, the geographic distribution range of some parasite lineages mirrors that of A. sylvaticus lineages in SW Europe, and that of A. flavicollis lineages in the Balkans and in the Middle East. Thus, regional co-differentiation likely occurred between the parasite and the two sister Apodemus hosts in different parts of their distribution range. We suggest that differences in regional abundances of A. sylvaticus and A. flavicollis are responsible for generating this pattern of regional co-differentiation. This study highlights the importance of integrating both geography and biogeographic information from potential hosts to better understand their parasite phylogeography.

Carboplatin, methotrexate, and vinblastine in patients with bladder cancer who were ineligible for cisplatin-based chemotherapy

Background. A Phase II trial with a new regimen of methotrexate, carboplatin, and vinblastine (M‐CAVI) was conducted for patients with bladder cancer who could not receive cisplatin‐based chemotherapy.

WHERE ARE THE WORMY MICE? A REEXAMINATION OF HYBRID PARASITISM IN THE EUROPEAN HOUSE MOUSE HYBRID ZONE

Wormy mice in a hybrid zone have been interpreted as evidence of low hybrid fitness, such that parasites contribute to species separation. However, because of its natural heterogeneity, observations of parasite load must be numerous with good field area coverage. We sampled 689 mice from 107 localities across the Bavaria‐Bohemia region of the European house mouse hybrid zone and calculated their hybrid indices using 1401 diagnostic single nucleotide polymorphisms (SNPs). We tested whether hybrids have greater or lesser diversity and load of parasite helminths than additive expectations, performing load analyses on the four most common taxa. We found hybrids have significantly reduced diversity and load of each of the commonest helminths; rarer helminths further support reduced load. Although within‐locality comparisons have little power, randomization tests show the repeated pattern is unlikely to be due to local parasite heterogeneity, and simulations show a patch of low parasite diversity is unlikely to fall by chance just so in the field area, such that it produces the observed effects. Our data therefore contradict the idea that helminths reduce hybrid fitness through increased load. We discuss a vicariant Red Queen model that implies immune genes tracking parasites will escape Dobzhansky–Muller incompatibilities, generating hybrid variants untargeted by parasites.

Five-day course of granulocyte colony-stimulating factor in patients with prolonged neutropenia after adjuvant chemotherapy for breast cancer is a safe and cost-effective schedule to maintain dose-intensity.

PURPOSE To analyze the safety and efficacy of a short course of granulocyte colony-stimulating factor (G-CSF) to maintain dose-intensity of subsequent cycles of chemotherapy after a prior episode of prolonged neutropenia, without febrile complications, in patients receiving adjuvant treatment for breast cancer. PATIENTS AND METHODS Thirty-two patients undergoing adjuvant cyclophosphamide, methotrexate, and fluorouracil (CMF) or doxorubicin-CMF for stages I to II breast cancer were included after having chemotherapy delays due to neutropenia (absolute neutrophil count [ANC] < 1.5 x 10(9)/L) on day 22. G-CSF was administered subcutaneously on days 15 to 19 of each subsequent cycle. RESULTS None of the patients included in this study had to be admitted to the hospital for fever and neutropenia. The median percentage of the projected dose-intensity for CMF or doxorubicin-CMF on an intent-to-treat basis was 0.994, which was significantly higher than the delivered dose-intensity before the start of G-CSF treatment (P < .0001). Patients who received concomitant G-CSF and radiotherapy achieved a similar dose-intensity as patients who did not undergo radiotherapy. Seven patients discontinued G-CSF treatment due to musculoskeletal pain. These patients had more subsequent cycle delays because of day 22 neutropenia than the 25 patients who followed the G-CSF schedule (P = .0028). CONCLUSION A 5-day course of G-CSF in patients with prior chemotherapy delays due to prolonged neutropenia seems to be a safe and cost-effective schedule to maintain CMF or doxorubicin-CMF dose-intensity in the adjuvant treatment of breast cancer.

Helminth communities of the exotic introduced turtle, Trachemys scripta elegans in southwestern Spain: Transmission from native turtles

We report the prevalence and diversity of helminth parasites found in native turtles Mauremys leprosa and Emys orbicularis from three localities in southwestern Spain and we describe the helminth communities of exotic turtles Trachemys scripta elegans coexisting in the wild with both native turtle species. Five nematodes species were identified, of which Serpinema microcephalus was the only species common between two localities, although infection parameters were different between them. This is the first report of cross transmission of S. microcephalus and Falcaustra donanaensis from native to exotic turtles and the first report of genus Physaloptera in turtles of the Palearctic Region. Continuous releasing of exotic pet turtles in wildlife ecosystems increases the risk of parasite introductions and, consequently, potential transmission to native species, and highlights the impending need for regulation of pet turtle trade in Europe.

Host-parasite network structure is associated with community-level immunogenetic diversity

Genes of the major histocompatibility complex (MHC) encode proteins that recognize foreign antigens and are thus crucial for immune response. In a population of a single host species, parasite-mediated selection drives MHC allelic diversity. However, in a community-wide context, species interactions may modulate selection regimes because the prevalence of a given parasite in a given host may depend on its prevalence in other hosts. By combining network analysis with immunogenetics, we show that host species infected by similar parasites harbour similar alleles with similar frequencies. We further show, using a Bayesian approach, that the probability of mutual occurrence of a functional allele and a parasite in a given host individual is nonrandom and depends on other host-parasite interactions, driving co-evolution within subgroups of parasite species and functional alleles. Therefore, indirect effects among hosts and parasites can shape host MHC diversity, scaling it from the population to the community level.

Endoparasite species richness of Iberian carnivores: influences of host density and range distribution

Abstract.We investigate the determinants of macroparasite species richness of Iberian carnivores. For this, we used the parasitological data collected on 14 species of carnivores over a 10-year period. These previously unpublished data permitted to estimate parasite species richness using estimators of species richness, i.e. Jackknife first order and Chao 2. Most of the parasite species were rare, with low prevalence. Potential determinants were investigated as possible factors explaining the variability of parasites species richness among carnivores host body mass, host geographical range, host longevity and host density. Using independent contrasts, we found positive relationships between residuals of estimates of parasite species richness and residuals in host density, and between residuals of estimates of parasite species richness and residuals in host range. These results are discussed in terms of risk of extinction and invasion abilities related to a possible investment in immune defences correlated with parasite diversity.

Is there sex-biased resistance and tolerance in Mediterranean wood mouse (Apodemus sylvaticus) populations facing multiple helminth infections?

Sex-biased parasitism is rarely investigated in relation to host tolerance and resistance, which are two defense strategies hosts can adopt when challenged by parasites. Health or fitness deteriorations in less tolerant individuals with increasing parasite burden would be faster than those in more tolerant ones. Hence, the body condition and reproductive potential of an infected individual host can be considered proxies for tolerance to parasitism. We studied Mediterranean populations of the wood mouse (Apodemus sylvaticus) and its helminth parasites. We assessed their resistance using the phytohemagglutinin test and spleen size, and their tolerance using body condition in males and females and testes mass in males. In order to avoid spurious correlations, we took into account the phylogeographic structure of the Mediterranean wood mouse populations. We used a mixed model adapted from the animal model used in quantitative genetics. While helminth infection did not differ between the two sexes, females and males differed in their measured defenses. Females seem to invest more in immune defense with increasing risk of parasite diversity, but also appear to be potentially more tolerant of parasitic diversity. These results suggest the existence of sexual differences in resistance and tolerance, and that measurements of parasitic loads alone could be insufficient to detect any underlying sexual differences in the two strategies that have evolved in response to multiple parasitic attacks.

HELMINTHS OF THE WILD RABBIT (ORYCTOLAGUS CUNICULUS) IN MACARONESIA

Two hundred and four rabbits from 8 Macaronesian islands (Pico, San Jorge, San Miguel, Terceira, and Flores from Azores Archipelago; Tenerife and Alegranza from Canary Islands; and Madeira from Madeira Archipelago) were examined for helminth parasites between 1995 and 2000. Three species of cestodes, Taenia pisiformis (larvae), Andrya cuniculi, and Mosgovoyia ctenoides, and 5 species of nematodes, Trichuris leporis, Graphidium strigosum, Trichostrongylus retortaeformis, Passalurus ambiguus, and Dermatoxys hispaniensis, were identified. Only 3 species (M. ctenoides, T. retortaeformis, and P. ambiguus) were regularly distributed over the 3 archipelagos. Taenia pisiformis was not collected in Madeira, nor was A. cuniculi in the Azores and G. strigosum in the Canary Islands. Trichuris leporis and D. hispaniensis were only found in Madeira. Significant differences in the general prevalence of the nematodes G. strigosum and T. retortaeformis were detected between Azores and Madeira. The prevalence of T. retortaeformis differs significantly between the Azores and the Canaries and that of P. ambiguus was higher in Madeira than in Azores and Canaries. The helminth richness found in the wild rabbit in these Macaronesian archipelagos was very low compared with the Palearctic helminth fauna of this host. The wild rabbit was introduced from the Iberian Peninsula into different Macaronesian islands. Helminths introduced with Oryctolagus cuniculus into these islands also are commonly found in Iberian wild rabbits, which are excellent colonizers, as demonstrated in this study.

Habitat fragmentation alters the properties of a host-parasite network: rodents and their helminths in South-East Asia

1. While the effects of deforestation and habitat fragmentation on parasite prevalence or richness are well investigated, host-parasite networks are still understudied despite their importance in understanding the mechanisms of these major disturbances. Because fragmentation may negatively impact species occupancy, abundance and co-occurrence, we predict a link between spatiotemporal changes in habitat and the architecture of host-parasite networks. 2. For this, we used an extensive data set on 16 rodent species and 29 helminth species from seven localities of South-East Asia. We analysed the effects of rapid deforestation on connectance and modularity of helminth-parasite networks. We estimated both the degree of fragmentation and the rate of deforestation through the development of land uses and their changes through the last 20 to 30 years in order to take into account the dynamics of habitat fragmentation in our statistical analyses. 3. We found that rapid fragmentation does not affect helminth species richness per se but impacts host-parasite interactions as the rodent-helminth network becomes less connected and more modular. 4. Our results suggest that parasite sharing among host species may become more difficult to maintain with the increase of habitat disturbance.